Drying process and apparatus



July 15 1924. 1

' T. BOBERG DRYING PROCESS AND APPARATUS Filed May 19, 1920 2 Sheets-Sheet l I I 9% N I :zzzzz-Jf I 1 INVENTUR BY TBobevy ATTORNEY July 15 1924.

T. BOBERG DRYING PROCESS AND APPARATUS Filed May 19. 1920 2 Sheets-Shem 2 INVENTOR Tfiabery MM ATTORNEY Patented July 15, 1924.

UNITED STATES PATENT OFFICE.

TEOFRON BOIBERG, OF CLAPHAM PARK LONDON, ENGLAND, ASSIGNOR TO TECHNO- CHEMICAL LABORATORIES, LIMITED, OF GLAPHAM PARK, LONDON, ENGLAND.

DRYING PROCESS AND APPARATUS.

Application filed May 19, 1920. Serial No. 382,521.

To all whom it may concern:

Be it known that I, TEOFRON BoBEno, a subject of the King of GreatBritain and Ireland, and residing at F airlawn, Clarence Road, Clapham Park, London, S. W. 4, England, have invented certain new and useful Improvements in or Relating to Dryin Processes and Apparatus, of 'which the 0 lowing is a specification.

This invention relates to the drying of material comprising solid matter in combination or admixture with liquid, say for example, peat pulp.

n co-pending application Serial No. 358,088 there is described a method of drying material of a high water content in two or more stages by means of a revolving drum headed by the evolved vapour after its temperature has been raised a few degrees by compression, the drum bein arranged first to pick up a thin layer 0 the moist material on its circumferential surface and then to transfer it in a partially dried state to other apparatus having similarly heated drying surfaces, the capacity and arrangement of which is suflicient to reduce still further the water content of the material before its final removal therefrom.

It has also been proposed in various prior specifications to dry peat pulp froma water content in the neighborhood of 94% down to a water content, say, of some 10% or less in two or more stages, by various methods, said methods for example comprising filter pressing, band pressing and conveyance in contact with or in suspens1on in a heated gaseous medium.

The object of the present invention is to combine advantageous features of the foregoing proposals.

The invention consists in a method of dryin pulpy or other material having a high liquid content in two or more stages, accordingto which said materlal 1s first treated upon drying surfaces heated by the evolved vapour raised by compressmn to a higher temperature, and is then further dried; during conveyance or .SUSPGIISIOII 1n a moving heated gaseous medium.

The invention further consists in a method according t the preceding paragraph in which material of high water content, say for example peat pulp, is first deposited as a thin layer upon a surface heated by the evolved vapour after its temperature has been raised, a small amount by compression, and the resulting partially dried matter is brought to any further desired degree of dryness, while in suspension in hot flue gases or the like in motion in conveying tubes or like conduits.

The invention also consists in improved methodsof, or the combination of apparatus for drying material of high liquid content as hereinafter described.

. The accompanying diagrammatic drawlngs illustrate some convenient sets of appliances for carrying the inventioninto efect.

In these drawings:

Figure 1 shows a complete installation with a screw conveyor for moving the material in the second stage, and

Figures 2 and 3 show another known form of apparatus for conducting the second stage.

In accordance with this invention when operated in one convenient form, raw peat at ordinary temperature and having a water content in the neighbourhood of 94% is delivered as described in my co-pending application No. 358,088 by a suitable pump a through a surface contact heat Interchanger b heated by water and a surface contact heat interchanger a heated by steam into a direct contact heater (1 from which it passes to a trough e by means of which it is applied to the surface of a drum f mtating in a sealed casing 9.

Within thecasing g and adjacent to the trough is a second overflow trough t for collecting any wet pulp which may fall from the drum and for returnin it, together with a constant overflow rom the trough e, by means of the pump u into the direct contact heater d to maintain by cir culation a uniform condition of the pulp in the trough e.

Into the interior of the drum'f steam, say at a temperature of about 1059C. 1s delivered by a compressor It which draws the steam evolved on the outer surface of the drum f atabout 100 C. from the casing'g and raises its temperature b the necessary small amount of, say, 5 by compression. A

Within the casing g in contact with the downwardly moving side of the drum f are scrapers i which remove the more or less dried matter from the surface of the drum prior to its re-entering the trough e and deliver it by means of a collecting hopper j to the second stage of the process as hereinafter more fully described.

Power for the installation is conveniently derived from a boiler n supplying steam, say at 20 kilogrammes or square centimetre and 216 C. which is iilrther heated in the superheater o to a temperature of 360 C. and then passes to a turbine p for supply ing power t the installation, a connection .9 controlled by the valve 9' from one stage of the turbine conveying steam at '10 kilogrammes per square centimetre and 266 C. to the cylinder 7' of a briquetting press m, the exhaust from which at a temperature of 105 C. may also be carried to the drum A further supply pipe 8 with valve 8' 1s also taken from a lower stage in the turblne tosupply steam at 105? C. to the drum '7 when required for starting, make up or other purposes.

The condensed water from the drum f passes by a connection '0 and steamtrap '0' to the hot water heater 6 from which it is finally rejected at a temperature, say in the neighbourhood of 20 C. after heating the rawpeat. The condensed steam from the steam heater 0, also passes by way of the connection wand steam trap w to the water heater b;

Steam at 105 C. may be taken from the drum f by means of a connection a: to the surface contact steam heater 0, and any steam not condensed therein may, under control of the valve y be returned through the connection 2 and be further utilized in the direct contact heater (1 from which it is finally rejected through the pipe 1, say at a temperature of 92 C. for thepurpose of removing the air and fixed gases, the peat after passage through the hot water heater 6 and surface contact heater 0 being dolivered to the direct contact heater d at a temperature of about 90 C. and passing therefrom by the connection 3 into the trough e at a temperature of 100 C.

A layer or film of the peat pulp is taken up by the surface of the drum 7- as it moves through the pulp in the trough e and said film remains closely adherin to the surface as the vapour is'driven o and until the more or less dried solid matter is removed by the scrapers i.

In the specification of patent No. 1,501,513, July 15, 1924 partially dried material removed from a drum passes to a second stage comprising further evaporating surfaces heated by" compressed vapour, but in certain industries, and particularly in the utilization of peat, a supply of heating medium is often available in the shape of flue gases from boiler or other furnaces or exhaust gases from gas engines or the like.

resent invention parof 1911and 17,426 of 1912, the drying being 1 carried to any desired degree of completeness in one or more stages, and in accordance with the use to which the dried material is to be put.

When the second sta e is to be effected during conveyance as s own in Figure 1, the material entering the hopper j is transferredv into an extended conveyor conduit k in the lower portion of which there is positioned a rotating helix or screw k which carries the more or less powdered material along the conduit in contact with the flue gases from the boiler n and superheater 0, saidgases entering by the pipe 0" and passing along the upper portion of the conduit which they leave by the pipe 0 The screw keeps the material in a disturbed condition during its passage along the conduit 7:, and thus the heated flue gases come into intimate contact with all the particles and effect a very thorough drying.

The material which may enter the conduit with a watercontent, say in the neighbourhood of about 30%, may be dried by the hot gases down to a water content, say of about 9% in which condition it may be delivered to the hopper m of the briquetting press m.

In another way of carrying out the invention, the material from the hopper may enter through any suitable proportion device, the connection 4 of a flue 5 through which gases from a boiler furnace or other source are drawn by means of an exhauster 6. The exhauster delivers the gas in which the more or less powdered material is now suspended into an extended pipe or conduit 7, from whence it is delivered to cyclone separating devices 8 positioned over the hopper or collecting bin 9 of a briquetting press or any other convenient appliance. This arrangement is similar to that described in British Patent No. 24,748 of 1911, and if desired the powdered material may be treated in two lengths of conduit with return of the partly cooled gases as described iii British Patent No. 17,426 of 1912.

Material fortreatment in suspension in a current of heated medium may be driedto any suitable water content which will permit sub-divided matter resulting the material to assume a powdered or disintegrated condition, and in the treatment of peat it has been found convenient to dry the material to a water content in the neighbourhood of from 30% before removing it from the drying drum and delivering it to the hopper j, and .to then complete the drying from this point down, say, to about 9% before delivering it to the hopper 9.

It is to be understood that the drum apparatus hereinbefore indicated may be replaced by any other suitable apparatus for carrying out the vapour compression method of evaporating drying, also that other means may be adopted for completing the second stage of the process by drying during conveyance or suspension in a eated moving gaseous medium, and that either stage may if desirable be conducted in two or more types of apparatus.

Other additions and modifications may also be made without in any way departing from the spirit of this invention.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. A method of drying material to be used for industrial purposes in stages b energy generated from the combustion of e1, consisting in generating products of combustion, evolving vapour from the moist material upon a drying surface, utilizing part of the energy of said products of combustion to raise the temperature of said vapour by compression, heating the drying surface by applying said compressed vapour thereto and removing partly dried material from said drying surface, and mingling it with products of combustion of which part of the energy has been already utilized in order to complete the drying operation.

2. Apparatus for drying material in stages by energy generated from the combustion of fuel, comprisin in combination means for generating pro ucts of combustion, means for converting part of the heat of said products into mechanical work, a

heat transmitting partition, one side of which constitutes a drying surface, means for utilizing said mechanical work to draw" off vapour generated upon the drying surface and after raising its temperature by compression returning it as heating medium to the other side of the partition, a conduit along which the roducts of combustion pass after conversion of part of their heat into mechanical work and means for removing partly dried material from the drying surface and introducing it into said conduit to complete a further stage of the drying by the heat of said products of combustion.

3. Apparatus for drying material in stages by the energy generated from the combustion of fuel, comprising in combmation a furnace for heating a boiler which supplies steam, an enclosed drying drum, means operated by said steam for withdrawing the vapour evolved on the exterior of the drum and returning it at a higher temperature and pressure to the interior thereof, a conduit along which flue gases pass from said boiler and means for removing the matter treated upon the drum drier and mingling it with the flue gases to effect a further stage of the drying operation.

4. A concentration and drying apparatus for reutilization of latent heat comprising a fuel combustion apparatus a moving heat transmitting partition, means forcapplying to one side of said partition an adhesive film of heated material, means for collecting the vapor given off by said heated material and for raising the temperature of said vapor by compression and returning it as the heating medium to the other side of said partition, and means to separate the material from said partition and mix it with the products of combustion from'said fuel combustion apparatus.

5. A concentration and drying apparatus for expelling vapor from material by the reutilization of latent heat, comprising a fuel combustion apparatus a moving heat transmitting partition, means for pressing the film of material onto one surface of said partition to cause it to adhere thereto, means for collecting the vapor given ofi by the said film of material and for raising the temperature of said vapor by compression and returning it as a heating medium to the other side of said partition, and means to separate the material from said partition and mix it with the products of combustion from said fuel combustion apparatus.

6. A method of drying material used for industrial purposes in a plurality of stages by energy obtained from the combustion of fuel consisting in utilizing a portion of heat given off by the combustion to produce mechanical work and utilizing the work for compressing the vapors given off in the first stages of the drying process, employing the compressed vapors as a heating medium for one stage of the drying process, conveying away th partially dried material and mixing it with the products of combustion to effect the later stages of the drying process.

7. A method of evaporativc drying of peat pulp having a large water content in a plurality of stages by energy obtained from the combustion of fuel, consistln 1n utilizing a portion of the heat produce by the combustion to compress the vapors given off in the first stages of the drying process, utilizing the compressed vapors to reduce the water content of the pulp to about 30%, then mixing the partially dried compressed vapors to heat the exterior surface. of a revolving drum on which surface the material is carried, removing the partially dried material from the drum and mixing it with the products of combustion to further dry the material.

In testimony whereof I have'signed my name to this specification.

TEOFRON BoisERG. 

